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- A dry electrode for EEG recording.
Taheri BA, Knight RT, Smith RL.
BioMedical Engineering Graduate Group, University of California at Davis 95616.
This paper describes the design, fabrication and testing of a prototype dry surface electrode for EEG signal recording. The new dry electrode has the advantages of no need for skin preparation or conductive paste, potential for reduced sensitivity to motion artifacts and an enhanced signal-to-noise ratio. The electrode's sensing element is a 3 mm stainless steel disk which has a 2000 A (200 nm) thick nitride coating deposited onto one side. The back side of the disk is attached to an impedance converting amplifier. The prototype electrode was mounted on a copper plate attached to the scalp by a Velcro strap. The performance of this prototype dry electrode was compared to commercially available wet electrodes in 3 areas of electroencephalogram (EEG) recording: (1) spontaneous EEG, (2) sensory evoked potentials, and (3) cognitive evoked potentials. In addition to the raw EEG, the power spectra of the signals from both types of electrodes were also recorded. The results suggest that the dry electrode performs comparably to conventional electrodes for all types of EEG signal analysis. This new electrode may be useful for the production of high resolution surface maps of brain activity where a large number of electrodes or prolonged recording times are required.
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Here is another Reprirnt regarding Scalp EEG Electrodes:
Scalp electrode impedance, infection risk, and EEG data quality
Thomas C. Ferree, Phan L. Luu, Gerald S. Russell, Don M. Tucker
Objective: Breaking the skin when applying scalp electroencephalographic (EEG) electrodes creates the risk of infection from blood-born pathogens such as HIV, Hepatitis-C, and Crutzfeld-Jacob Disease. Modern engineering principles suggest that excellent EEG signals can becollected with high scalp impedance (» 40 kΩ) without scalp abrasion. The present study was designed to evaluate the effect of electrode-scalp impedance on EEG data quality.Methods: The first section of the paper reviews electrophysiological recording with modern high input-impedance differential amplifiers and subject isolation, and explains how scalpelectrode impedance influences EEG signal amplitude and power line noise. The second section of the paper presents an empirical test of EEG data quality as a function of scalp-electrode impedance for the standard frequency bands in EEG and ERP (event-related potential) recording. Results: There was no significant change in amplitude of any EEG frequency as scalp-electrode impedance increased from less than 5 kΩ (abraded skin) to 40 kΩ (intact skin). As expected, 60 Hz noise increased linearly as a function of the absolute impedance and impedance mismatch between the measurement and reference electrodes. Conclusion: With modern high input-impedance amplifiers and accurate digital filters for power line noise, high-quality EEG can be recorded without skin lesions.
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Psychiatry and Clinical Neurosciences (2001), 55, 305310
Proposed supplements and amendments to A Manual of Standardized Terminology,Techniques and Scoring System for Sleep Stages of Human Subjects, the Rechtschaffen & Kales (1968) standard
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